Contemporary moisture vapor permeable tapes, such as medical tapes, frequently involve the combination of two principal layers--a "breathable" backing layer, and an adhesive layer, generally a pressure-sensitive adhesive, useful for applying that backing layer to the skin.
A number of conventional medical tapes have relatively rigid backings, and are therefore amenable to being dispensed in the form of linerless rolls or in pads, e.g., as disclosed in (co-pending U.S. application Ser. No. 732,587, filed May 10, 1985). The tape in such a roll or pad is typically made up of a backing layer, a pressure-sensitive adhesive layer and optionally, if necessary, a low adhesion backsize ("LAB") material applied to the backing of the tape, i.e., on the side opposite that bearing adhesive, to allow the roll to be easily unwound, or to facilitate the separation of one pad sheet from another.
The use of LAB materials to improve the release characteristics, i.e., increase the ease of separation, of tapes has been described previously, e.g., in U.S. Pat. Nos. 2,532,011 and 3,318,852. LAB's have been applied to backings as the only coating in a one-pass coating operation, e.g., as described in the '011 patent. LAB's have also been applied as the second coating of a two-pass coating operation, e.g., wherein a fibrous backing is first coated with another material such as a fiber-binding and/or filling material which is then dried and followed by an LAB material applied as a second coating, e.g., as disclosed in the '011 patent as well as in U.S. Pat. No. 3,121,021.
The use of an LAB material in a blend with a compatible or an incompatible "non-tacky high polymer" are mentioned in '011 patent as expedient means of lowering the amount of LAB needed, thereby lessening the cost of its use.
In contrast to the above-described tapes having relatively rigid backings, there are a variety of tapes that have not to date been dispensable in the form of linerless rolls or in pads in a manner that does not compromise desirable inherent properties of the backing. Such tapes typically have fabric backings that exhibit a variety of desirable properties for medical use, such as softness and conformability, as well as moisture vapor permeability. Such fabrics are generally easily extensible as well, in that they can be extended in length or width by tension. Unfortunately however, such fabrics are also typically inelastic, i.e., exhibit little or no retractive forces when extended. As a result, the fabrics will not return to their original shape when the tension is released.
U.S. Pat. No. 4,366,814 describes the impregnation of such extensible backings with elastomers in order to impart elasticity to the backings, thereby allowing the use of the resultant backings, e.g., as stretch bandages and as backings for adhesive tapes. The tapes made from extensible fabrics that have been impregnated with elastomer must frequently be dispensed using liners however, since the backings are still generally deformable by the forces that would be required to pull them from a linerless roll or pad. The need for a liner, however, adds time, cost and inconvenience to the manufacture and use of such tapes.
The use of an LAB material applied as the second coat in a conventional two-pass coating operation, i.e., after elastomer, may enable such tapes to be dispensed without a liner from a roll or pad, but frequently is accompanied by a compromise of some or all of the very properties for which the backing was chosen such as moisture vapor permeability, softness and/or conformability, or else the backing exhibits insufficient release characteristics and/or elasticity.
As a result, in spite of the drawbacks associated with their use, liners have still been generally preferred for use with many elastomer-impregnated tapes, as opposed to the use of linerless tapes with LAB coatings.